Since the first isolation of camptothecin from the wood and bark of Camptotheca acuminata by Wall and co-workers [M. E. Wall et al., J. Am. Chem. Soc., 88, 3888 (1966)], there had been many approaches to synthesize camptothecin. However, the development of camptothecin as an effective antineoplastic agent was unsuccessful due to its severe toxicity in the clinical trial in 1970. Thereafter, Liu et a reported in 1985 that camptothecin had a specific mode of action to inhibit topoisomerase I. Thus, considerable interest has focused on this compound.
Recently, various studies for the development of camptothecin derivatives have been proposed in order to reduce the toxicity of camptothecin and to further enhance its antineoplastic activities. Among these related studies, the clinical trial of CPT-11 (irinotecan) synthesized by Yakurt-Honsha Co. of Japan in 1986 showed that it exhibited excellent antineoplastic activities with less toxicity (Japanese Patent Laid Open Publication No. 64-61482) and followed by other pharmaceutical companies such as Smithkline Beecham (topotecan) and Glaxo (MDO-camptothecin and 9-amino camptothecin). Among them, CPT-11 and topotecan are launched.
On the other hand, the present inventors have reported the 7-aminoethyl camptothecin derivatives and manufacturing process thereof through the total synthesis, which have strong antitumor activity, weak toxicity, and broad safe region, in Korean Patent Application No. 95-269 and 96-248.
The above invention produces camptothecin derivatives that have strong antitumor activity. However, the procedure of manufacturing those is complex since the total synthesis is adopted and since intermediate material used is a new one. Consequently, there has been a strong need to develop a simple and convenient manufacturing process of camptothecin derivatives for mass production.
Accordingly, the inventors et al. have studied a convenient process by which camptothecin derivatives having excellent activities can be manufactured from a compound of general formula 2 such as (S)-7-methylcamptothecin [S. Sawada et al., Chem. Pharm. Bull., 39 (1991) 2574.about.2580]. Thus, the present invention has been completed.